The object of this proposal is the identification and initial biochemical characterization of cell surface constitutents on spermatogenic cells and on Sertoli cells which are involved in the interactions of these cells during mammalain spermatogenesis. In particular, we are examining the cell surface events modulation two factors of cellular interactions within the seminiferous epithelium. First, we are examining the specific in vitro adhesion of Sertoli cells in isolated preparations of seminiferous tubule basement membrane. Second, we are examining the specific binding of purified mouse germ cells to Sertoli cell monolayers, using an in vitro assay recently developed by this laboratory. Specific Aims include: (1) Biochemical characterization of the isolated seminiferous tubule basement membrane and comparisons with basement membranes from other sources, in order to identify specific molecules of the extracellular matrix responsibile for the easymmetric adhesion of Sertoli cells. Biochemical studies of the possible roles of specific receptor peptides from both fibronectin and laminin are planned. (2) Serological analysis of isolated Sertoli cell plasma membranes, using polyclonal antisera, in order to idenitfy cell membrane receptors for basement membrane components. (3) Serological inhibition of the adhesion of spermatogenic cells to Sertoli cell monolayers. These experiments will involve purified populations of later germ cells, including pachytene spermatocytes and round spermatids. A library of monoclonal antibodies prepared against plasma membranes from these cells is already available. (4) Determination of the stage-specificity of germ cell adhesion to both extracellular matrix and to Sertoli cells. Results from these studies will aid our understanding of the physiological regulation of germ cell translocation within the seminiferous epitherlium and of the molecular mechanisms governing the interaction of Sertoli cells with their.